This paper presents a cluster structure, characterized by a set of structure parameters and a set of interconnection functions, as a conceptual interconnection scheme for large multimicrocomputer systems. It is shown that three popular interconnection structures (hypercube, hierarchy, and tree structures) are examples of the cluster structure. Two communication problems (traffic congestion and message delay), which may result in interconnection limitation to a particular structure, are analyzed. The analysis provides a way to understand structural properties such as complexity, capacity, and limitation. Through the use of the cluster structure and the analytical model, topological optimization is presented to show how interconnection limitation can be minimized.